Alexey Alexeyevich Oleynik (born June 25, 1977, as Oleksíy Oleksíyovych Olíynyk) is a Ukrainian-born Russian mixed martial artist, combat sambist and jujitsuka currently signed with the Ultimate Fighting Championship, competing in their heavyweight division. He began his professional fighting career in 1997, and is a veteran of M-1 Global, ProFC and IAFC and has competed for Bellator, KSW and YAMMA Pit Fighting. He is the only fighter to win a UFC fight via Ezekiel choke, and has done so twice. Oleynik also holds the record for most Ezekiel choke wins in MMA competition, with twelve. As of February 18, 2019, he is ranked #9 in official UFC heavyweight rankings.
During his training camp with K-Dojo Warrior Tribe in April 2011, Oleynik participated in two Grappling tournaments, he won the Absolute division in an Eddie Alvarez hosted grappling tournament, and also won the Men's black belt No-Gi Advanced Superweight (210 lbs and over) division in the Grapplers Quest "Beast of the East 2011" tournament.